In practice, the coupling angle emerges randomly. From EP 1 911 939 A1, it is known to select the coupling angle in a targeted manner. Using this, it is possible to select a coupling angle at which the vibration load is minimized. Roughly speaking, this renders it possible to compensate imbalances of the two turbines to a certain extent. This can obtain a reduction in the vibration load, particularly in comparison with a coupling in which the two turbines are coupled in such a way that imbalances add. Despite this advantage, this method is not employed.